US 7395448 B2
Information usable in determining the quality of time produced by a clock of a processing environment is obtained. The information is obtained directly by an application program absent use of a supervisor service, such as an operating system or operating system service. The application program invokes an instruction that returns a parameter block that includes the information.
1. A method of facilitating a determination of the quality of time produced by clocks of processing environments, said method comprising:
providing, by a clock of a central processor of the processing environment, a current time value and continuously updating by hardware of the processing environment the current time value, the processing environment comprising a supervisor service processing layer and an application program processing layer; and
issuing a request, by an application program running within the application program processing layer of the processing environment, for information usable in determining the accuracy of the time value relative to an external time standard, the request being made via a perform timing facility function instruction, wherein execution of the perform timing facility function selects desired information and places the information in a parameter block specified by the application program, the parameter block being located in memory of the processing environment at an address specified in a general register by the perform timing facility function instruction, the parameter block being directly accessible by the application program, and wherein the information is obtained by the application program absent use of a supervisor service of the supervisor service processing layer.
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This invention relates, in general, to timing facilities of processing environments, and in particular, to obtaining information useful in determining the quality of time produced by the timing facilities.
Processing environments have various timing facilities, including time of day (TOD) clocks that are used to provide a high resolution measure of real time suitable for the indication of date and time of day. Processes within a processing environment rely on the time produced by these timing facilities to ensure reliable and accurate execution of the processes within the processing environment.
Various protocols have been developed to handle different aspects relating to the timing facilities. For example, time protocols have been developed to manage the synchronization of time between different clocks within and outside of the processing environment.
As a further example, protocols have been developed that enable control programs (e.g., non-application level programs) to obtain information concerning the quality of time produced by the timing facilities. For instance, in the current zSeries® servers, offered by International Business Machines Corporation, the LPAR hypervisor has direct access to time quality information. However, this information is not directly available to application programs. If an application program desires this information, it invokes supervisor services to obtain the information. This is costly, inefficient, and requires additional overhead.
Based on the foregoing, a need exists for an efficient mechanism to enable application programs to directly obtain time quality information. For example, a need exists for a capability that enables application programs to directly access, without use of supervisor services, information usable in determining the accuracy of time values relative to Coordinated Universal Time (UTC).
The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a method of facilitating a determination of the quality of time produced by clocks of processing environments. The method includes, for instance, providing by a clock of a processing environment a time value; and obtaining, by an application program of the processing environment, information usable in determining the accuracy of the time value relative to an external time standard, wherein the information is obtained by the application program absent use of a supervisor service.
System and computer program products corresponding to the above-summarized method are also described and claimed herein.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.
One or more aspects of the present invention are particularly pointed out and distinctly claimed as examples in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
In accordance with an aspect of the present invention, a capability is provided for facilitating the determination of the quality of time provided by timing facilities of a processing environment. For example, information is obtained that is usable in determining the accuracy of time values provided by a clock (e.g., a time of day (TOD) clock) of the processing environment relative to an external time standard, such as Coordinated Universal Time (UTC). This information is obtained directly by an application program, without the application program needing to invoke or use a supervisor service. As used herein, a supervisor service includes any non-application level program or service, including, for instance, an operating system, a control program, an operating system service, a hypervisor, etc. The application program does not communicate with the supervisor service to obtain this information (i.e., obtain a control block including the information).
One example of a processing environment to incorporate and use one or more aspects of the present invention is described with reference to
A processing environment 100 includes, for instance, a processing unit 102 coupled to another processing unit 104 via a connection 106. Each processing unit is, for instance, a zSeries® server, offered by International Business Machines Corporation (IBM®). Connection 106 includes, for instance, one or more links, such as InterSystem Channel (ISC) links or Integrated Cluster Bus (ICB) links, offered by International Business Machines Corporation. In one example, the links employ a Server Time Protocol (STP), also offered by International Business Machines Corporation, to allow timing information to be passed between the processing units. IBM® and zSeries® are registered trademarks of International Business Machines Corporation, Armonk, N.Y., U.S.A. Other names used herein may be registered trademarks, trademarks or product names of International Business Machines Corporation or other companies.
Each processing unit includes, for example, a central processing unit 110 (
In this example in which multiple processing units are coupled to one another and each has its own clock, one of the clocks is selected to provide Coordinated Server Time (CST). This clock is relied upon in the processing environment to facilitate synchronization, etc. Further, this clock is useful in determining the quality of time produced by one or more of the clocks, as described below.
In accordance with an aspect of the present invention, information usable in determining the quality of timing information produced by a clock of the processing environment is obtained by an application program without the application program calling or using a supervisor service. The application program issues a request for the information (referred to herein as quality information), STEP 200 (
The request is made, in one example, via an instruction, which is further responsible for returning the information to the requesting application. This instruction, referred to herein as Perform Timing Facility Function (PTFF), is described in further detail with reference to
The PTTF-QUI function obtains information usable in determining the quality of time values produced by a clock of a central processor. In one example, the function locates the desired information in hardware system timing area 122 and places the information in a parameter block. The information in the hardware system timing area is continuously updated (e.g., every 64 ms) by the hardware of the processing environment, irrespective of whether a request is being made for the information. In particular, in one example, a timing network, such as STP, is used to transmit timing information between the various processing units of the processing environment. The hardware (e.g., millicode) of the environment uses this information and/or other information within the processing environment to update the information in the hardware system timing area. This information is then available for use by the PTFF-QUI function.
In response to invoking the instruction, the PTTF-QUI function selects the desired information from the hardware system timing area and places the information in the parameter block specified by the application program. The parameter block is located in memory by an address 322 (
One embodiment of the fields included in a UIB are described with reference to
UIB 400 includes information to convert from a time of day clock timestamp to primary reference time (PRT), and then from PRT to Coordinated Universal Time (UTC). The time of day clock timestamp is, for instance, a 64 bit unsigned binary number indicating the number of clock units since the TOD clock epoch.
Examples of how to convert from TOD to PRT, and from PRT to UTC are described below. In the examples, the following abbreviations and symbols are used:
To convert from a TOD clock timestamp to primary reference time, the following fields of the UIB are employed, in one embodiment:
In general, this conversion is represented by Tz=Tb+Dzb±Ezb, where Tb is a time value (e.g., 64-bit TOD value) obtained by issuing a STORE CLOCK instruction in the basic machine (or otherwise obtaining the TOD), Tz is the most likely corresponding primary reference time value, Dzb is the offset between Tz and Tb, and Ezb is the error bound (dispersion) for Tz.
More specifically, the conversion is computed, as follows: Tb+Dzb(T)−Ezb(T)≦Tz≦Tb+Dzb(T)+Ezb(T), where Dzb(T) and Ezq(T) are the PRT TOD Offset and PRT TOD Dispersion, respectively, at time T.
Expanding, the above inequalities become:
This expansion is based on the following:
To convert from primary reference time to UTC, in one embodiment, the following fields in the UIB are used: leap seconds update event time, old leap seconds, and new leap seconds fields. For a primary reference time less than the leap seconds update event time, the old leap seconds value applies; for a primary reference time equal to or greater than the leap seconds update event time, the new leap seconds value applies. The applicable leap second value is added to UTC to form primary reference time (PRT).
Described in detail above is a capability for efficiently obtaining information, directly by an application program, that is usable in determining the quality of time in relation to Coordinated Universal Time.
One or more aspects of the present invention can be included in an article of manufacture (e.g., one or more computer program products) having, for instance, computer useable media. The media has therein, for instance, computer readable program code means of logic (e.g., instructions, code, commands, etc.) to provide and facilitate the capabilities of the present invention. The article of manufacture can be included as a part of a computer system or sold separately.
One example of an article of manufacture or a computer program product incorporating one or more aspects of the present invention is described with reference to
A sequence of program instructions or a logical assembly of one or more interrelated modules defined by one or more computer readable program code means or logic direct the performance of one or more aspects of the present invention.
Advantageously, an application program is able to directly obtain information usable in determining the quality of time without having to invoke a supervisor service. This enables the information to be obtained more efficiently and more cost effectively.
Although various embodiments are described above, these are only examples. One or more variations can be made without departing from the spirit of the present invention. For instance, the processing environment may include only one processing unit or more than two processing units. Further, in yet another embodiment, one or more of the processing units is a central processing complex having one or more central processors, each central processor having a TOD clock. The central processor complex is logically partitioned, in one example, and includes one or more logical partitions. Further, processing environments based on architectures other than the z/Architecture can include one or more aspects of the present invention. Additionally, one or more of the processing units may be other than a z/Series® server. Yet further, information may be obtained relating to system clocks other than time of day clocks. Also, the timing information can be stored in areas of memory other than the hardware system timing area, or in storage.
Although in the example above, an instruction is performed in order to request and obtain the quality of time information, in other embodiments, an instruction may not be used. Yet further, in another example, one instruction may be used to invoke the request and another instruction may provide the requested information. Further, the term parameter block is not meant to be limiting in any way. Any type of block or data structure can be used to return the information. Yet further, the external time reference may be a reference other than Coordinated Universal Time. Further, although various fields and parameters are described, many variations are possible with these fields and parameters. Many other variations are also possible.
Again, although various embodiments are described herein, these are not meant to limit the scope of the present invention. Many variations may be made without departing from the spirit of the present invention.
As a further embodiment, an environment may include an emulator (e.g., software or other emulation mechanisms), in which a particular architecture or subset thereof is emulated. In such an environment, one or more emulation functions of the emulator can implement one or more aspects of the present invention, even though a computer executing the emulator may have a different architecture than the capabilities being emulated. As one example, in emulation mode, the specific instruction or operation being emulated is decoded, and an appropriate emulation function is built to implement the individual instruction or operation.
In an emulation environment, a host computer includes, for instance, a memory to store instructions and data; an instruction fetch unit to fetch instructions from memory and to optionally, provide local buffering for the fetched instruction; an instruction decode unit to receive the instruction fetch unit and to determine the type of instructions that have been fetched; and an instruction execution unit to execute the instructions. Execution may include loading data into a register for memory; storing data back to memory from a register; or performing some type of arithmetic or logical operation, as determined by the decode unit. In one example, each unit is implemented in software. For instance, the operations being performed by the units are implemented as one or more subroutines within emulator software.
Further, a data processing system suitable for storing and/or executing program code is usable that includes at least one processor coupled directly or indirectly to memory elements through a system bus. The memory elements include, for instance, local memory employed during actual execution of the program code, bulk storage, and cache memory which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution.
Input/Output or I/O devices (including, but not limited to, keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers. Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modems, and Ethernet cards are just a few of the available types of network adapters.
The capabilities of one or more aspects of the present invention can be implemented in software, firmware, hardware, or some combination thereof. At least one program storage device readable by a machine embodying at least one program of instructions executable by the machine to perform the capabilities of the present invention can be provided.
The flow diagrams depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted, or modified. All of these variations are considered a part of the claimed invention.
Although preferred embodiments have been depicted and described in detail there, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.